1. Field of the Invention
The invention relates generally to tremolo devices for stringed instruments. More particularly, the invention relates to a bearing system for supporting a floating bridge tremolo device incorporated in a guitar.
2. Description of the Related Art
Since the 1950's guitars incorporating tremolo devices have been popular, and the effect upon the sound of the guitar a musician can create using such a device has become an integral part of the vocabulary of the guitar. Presently most electric guitars sold have a tremolo device of some kind.
By far the most widely employed type is patterned after that originally invented by Leo Fender disclosed, for example, in U.S. Pat. No. 2,741,146 issued Apr. 10, 1956. As a player presses down on a lever arm or handle, for example, connected to a spring-counterbalanced or "floating" bridge pivotable on a knife-edged bearing, string tension is reduced, causing the pitch to drop or "go flat." Conversely, as the handle is pulled back away from the guitar, string tension is increased causing the pitch to increases or "go sharp." This functionality facilitates a vibrato effect for example. When the player releases the arm, the bridge returns to an equilibrium position or "in-tune" state due to the biasing effect of springs configured to counterbalance the tension of the guitar strings attached to the bridge.
So that this in-tune state can be achieved consistently, a pivot point bearing system is needed that is as friction-free as possible. Leo Fender's original design featured a six-screw knife-edge mount. An improved design was developed by Floyd Rose, as disclosed for example in U.S. Pat. No. 4,171,661. The Rose bearing system incorporates two bearing posts and two specially shaped knife edge bearing points on the bridge.
To maintain proper function of knife-edge pivots, tremolo bridge constructions are conventionally limited to hardenable materials such as hardenable steel alloys. The forces exerted by the combination of the tensioned strings and the counterbalancing springs can exceed 150 pounds. As can be appreciated, the sharper the knife edge (giving better performance) the greater the force per unit area applied at the knife edge bearing contacts which are of course very small in cross-sectional area when the knife edges are sharp. Even hardened steel alloys will eventually fail under the combination of high compressive forces applied, and the cyclic nature of force application due to the tremolo device being rocked back and forth, particularly under vigorous use.
New bearings eventually become dulled and friction increases, causing less than ideal performance in that the tremolo bridge does not consistently return to the precise "in-tune " position at rest. After a period of use the guitar cannot be made to play consistently in tune and consequently the tremolo device must be replaced. This is an expensive procedure.
As can be appreciated, conventional knife-edged designs are inherently problematic in that the better the knife-edge, which minimizes friction, the greater the force per unit area transferred across the bearing contact and the greater the chance for failure of the material from which the knife-edge bearing is made. Very hard materials are needed to resist the forces applied, but the harder the metal used is, generally speaking the less elasticity it has. Since the bearing action is inherently reciprocating, hardness at the expense of elasticity is undesirable. In sum, the conflicting aspirations of design criteria conspire to limit bearing life. This drives costs in terms of replacements needed upwards, and is not desirable.